A reference calibration method for mobile phone shell positioning hole size drift

Abstract

The application discloses a kind of reference calibration methods for the size drift of mobile phone shell positioning hole, it is related to mobile phone shell production technical field, comprising: obtaining the contour boundary data of multiple positioning holes on mobile phone shell, contour action energy field is established in the internal region of positioning hole, and according to the distance relationship of each position to contour boundary, distance potential field is constructed, and center probability field is generated;According to the energy variation continuity and propagation direction consistency of contour action energy field analysis positioning hole contour boundary each area, identify abnormal action area and carry out energy attenuation processing to abnormal action area.The application constructs contour action energy field and distance potential field in the internal positioning hole, and further generates center probability field, so that the effect of positioning hole contour structure on internal space can be expressed in the form of continuous field, so that the stable center position of hole region can be stably determined when the positioning hole contour appears ovalization or local anomaly.

Description

Technical Field

[0001] This invention relates to the field of mobile phone case manufacturing technology, specifically to a benchmark calibration method for addressing the drift of positioning hole dimensions in mobile phone cases. Background Technology

[0002] With the increasing automation of mobile phone case production, multiple positioning holes on the mobile phone case are usually used as product positioning references during the production, inspection and assembly process to establish a product coordinate system, thereby enabling subsequent operations such as size inspection, structural recognition and assembly positioning. In actual production, the vision inspection system usually obtains the outline of the positioning hole through image acquisition equipment, extracts the hole outline through edge recognition algorithm, and then calculates the center position of the positioning hole through geometric fitting, which serves as the product positioning reference. During long-term production, due to factors such as mold wear, machining tolerances, and material stress, the positioning holes on the phone case may gradually undergo changes in size or shape, such as a certain degree of ellipticization in the hole structure. At the same time, during actual processing, burrs, chipping, or local contour defects may also occur at the edges of the positioning holes. These factors can all lead to local abnormal changes in the contour structure of the positioning holes. In this case, the circle fitting or ellipse fitting method based on the edge point set may be affected by local contour abnormalities or overall shape changes when calculating the center position of the positioning hole. When a vision inspection system uses multiple positioning holes to establish a product coordinate reference, the calculated results of the center positions of different positioning holes may differ to some extent. These differences, when superimposed in the spatial relationship, may have a certain impact on the product reference coordinate system, such as causing a slight rotation or positional shift in the reference coordinate system. To improve the stability of the positioning reference, existing technologies typically perform data processing on the positioning hole contours or calculate the spatial relationship of the multiple holes to improve the stability of the positioning results. Therefore, how to obtain a stable product reference even when the size or contour structure of the positioning holes changes has become a problem that needs further research in the field of industrial vision inspection. Therefore, this invention proposes a reference calibration method for the drift of positioning hole size in mobile phone cases. Summary of the Invention

[0003] The purpose of this invention is to provide a reference calibration method for addressing the drift of positioning hole size in mobile phone cases, thereby solving the problems mentioned in the background art.

[0004] This invention can be achieved through the following technical solution: a reference calibration method for the drift of positioning hole size in mobile phone cases, comprising: Step 1: Obtain the contour boundary data of multiple positioning holes on the phone case, establish a contour action energy field in the internal region of the positioning holes, and construct a distance potential field based on the distance relationship from each position to the contour boundary. Generate the center probability field of the positioning holes based on the contour action energy field and the distance potential field. Step 2: Based on the energy field analysis of the contour effect, analyze the continuity of energy changes and the consistency of propagation direction in each region of the positioning hole contour boundary, identify abnormal action areas, and perform energy attenuation processing on the abnormal action areas to obtain the effective contour area. Step 3: Reconstruct the distance potential field based on the effective contour area, determine the distance balance area according to the degree of distance balance from each position inside the positioning hole to the contour boundary, and combine the center probability field to screen and obtain the probability center candidate points of each positioning hole. Step 4: Map the probability center candidate points of each positioning hole to a unified product coordinate space. Calculate the drift coupling relationship between the positioning holes based on the relative spacing, orientation, and center stability of each positioning hole, and generate multiple product reference candidate coordinate systems. Step 5: Determine the target product reference candidate coordinate system based on the spatial relationship deviation of the positioning holes and the center stability corresponding to each product reference candidate coordinate system. Calculate the coordinate offset and direction rotation based on the spatial relationship deviation between this coordinate system and the design product coordinate reference. Correct the coordinates of the probabilistic center candidate points of the positioning holes in the unified product coordinate space to obtain the calibrated mobile phone case product coordinate reference.

[0005] A further technical improvement of the present invention is that the establishment of the contour effect energy field in step one includes the following steps: The contour boundary data of the positioning hole is divided into contour segments according to the boundary connection relationship to obtain multiple contour segments, and the connection node relationship between each contour segment is determined. The topological continuity parameters of each contour segment are calculated based on the connection node relationship between each contour segment to characterize the degree of continuity of each contour segment in the overall contour structure. The length weight parameter corresponding to each contour segment is calculated based on the boundary arc length of each contour segment, and the length weight parameter is coupled with the topological continuity parameter to obtain the segment action weight corresponding to each contour segment. Each contour segment is used as an energy propagation unit. Segmented propagation is performed to the internal area of ​​the positioning hole according to the segment action weight. The energy propagation between adjacent contour segments is constrained according to the connection node relationship between each contour segment in order to suppress the diffusion effect of topologically discontinuous contour segments on the internal area. The segmented energy responses formed by each contour segment are superimposed to generate the contour effect energy field in the internal region of the positioning hole.

[0006] A further technical improvement of the present invention is that the generation of the central probability field in step one includes the following steps: The energy response gradient at each position inside the positioning hole is calculated based on the contour action energy field, and the distance response gradient at each position inside the positioning hole is calculated based on the distance potential field. The probability transfer direction corresponding to each position is determined based on the energy response gradient and the distance response gradient, and a probability transfer relationship matrix is ​​established in the internal region of the positioning hole. Based on the probability transfer relationship matrix, a neighborhood probability transfer calculation is performed in the area inside the positioning hole, so that the probability value of each position is progressively accumulated to the adjacent position according to the corresponding probability transfer direction; During the probability transmission process, the probability values ​​received at each location are accumulated and calculated, and the accumulated probability values ​​at each location are arranged according to their corresponding spatial locations to form a probability accumulation matrix; The probability density values ​​of each position inside the positioning hole are calculated based on the probability accumulation matrix, and the probability density change amplitude is calculated based on the spatial gradient relationship between the probability density values ​​of each position. The region where the probability density change amplitude is lower than the probability stability threshold is determined as the probability stable region. The central probability field of the internal region of the positioning hole is established based on the probability density values ​​of each location within the probability stable region.

[0007] A further technical improvement of the present invention is that the identification of the abnormal action area in step two includes the following steps: The closed traversal order around the boundary of the positioning hole is determined based on the connection node relationship between each contour segment, and the boundary energy response sequence corresponding to each contour segment along the closed traversal order is obtained based on the contour action energy field. Perform forward closure tracing on each contour segment according to the closure traversal order, and perform reverse closure tracing according to the connection node relationship between each contour segment to obtain the forward closure sequence and reverse closure sequence corresponding to each contour segment; Calculate the node consistency, arc continuity, and position overlap based on the forward and reverse closure sequences corresponding to each contour segment, and calculate the self-consistent closure parameters of each contour segment based on the node consistency, arc continuity, and position overlap. Calculate the cooperative stability parameters between each contour segment based on the closure traversal order and the connection node relationship between adjacent contour segments; The closure anomaly parameters of each contour segment are calculated based on the self-consistent closure parameters and the cooperative stability parameters. The abnormal contour segment is determined based on the comparison between the abnormal closure parameter and the closure threshold, and the corresponding abnormal action area is determined based on the spatial position of the abnormal contour segment on the boundary of the positioning hole contour.

[0008] A further technical improvement of the present invention is that the energy attenuation treatment of the abnormal action area in step two includes the following steps: The isolation boundary surrounding the abnormal action area is determined based on the spatial position of the abnormal action area on the boundary of the positioning hole, and a local isolation zone for abnormal energy is established based on the area between the isolation boundary and the abnormal action area. Based on the distribution location of the abnormal energy local isolation zone in the contour action energy field, the energy propagation path from the abnormal action area toward the interior region of the positioning hole is restricted, while the energy propagation path along the contour boundary of the positioning hole is retained; The energy guiding boundary is determined based on the non-abnormal contour boundary region adjacent to the abnormal action region, and the propagation direction of the abnormal energy is determined based on the continuity of the energy response of the energy guiding boundary in the contour action energy field. Based on the propagation direction, the energy response within the local isolation zone of abnormal energy is transferred to the corresponding non-abnormal contour boundary region. The energy propagation path of each region of the positioning hole contour boundary is updated based on the transferred energy response to obtain the updated contour action energy field.

[0009] A further technical improvement of the present invention is that the determination of the distance equalization region in step three includes the following steps: The distance response values ​​corresponding to each position inside the positioning hole are obtained based on the reconstructed distance potential field, and multiple distance equivalence regions are determined based on the distance distribution relationship formed by the distance response values ​​in the region inside the positioning hole. Based on the spatial continuity and closed distribution relationship of each distance equivalence region within the positioning hole area, the corresponding distance closed loop structure is determined; Calculate the ring stability parameters corresponding to each distance closed loop structure based on the distribution range of each distance closed loop structure along the internal region of the positioning hole; Calculate the inter-loop consistency parameters based on the spacing variation relationship between adjacent closed-loop structures; The distance structure stability region is determined based on the ring stability parameters and the inter-ring consistency parameters, and the distance structure stability region is defined as the distance equalization region inside the positioning hole.

[0010] A further technical improvement of the present invention is that the generation of multiple product reference candidate coordinate systems in step four includes the following steps: Obtain the outer contour boundary data of the phone case, extract the boundary line segments on the phone case frame based on the outer contour boundary data, and determine the reference direction of the phone case frame based on the extension direction of the boundary line segments. Project the probability center candidate points of each positioning hole along the reference direction of the phone case frame, determine the arrangement order of each positioning hole according to the projection position of each probability center candidate point, and calculate the spacing change between adjacent positioning holes according to the projection spacing between adjacent probability center candidate points. The displacement direction and displacement amount of each positioning hole are calculated based on the positional deviation between the candidate probability center point of each positioning hole and the designed positioning hole position. The processing drift trend of each positioning hole along the reference direction of the mobile phone case frame is determined based on the arrangement order, spacing change, displacement direction and displacement amount. The drift coupling relationship between the positioning holes is determined based on the relative spacing, directional relationship, center stability, and machining drift trend among the positioning holes. Multiple product reference candidate coordinate systems are generated based on the drift coupling relationship, and the directional deviation between each product reference candidate coordinate system and the reference direction of the phone case frame is calculated. The arrangement order of each product reference candidate coordinate system is determined based on the directional deviation.

[0011] A further technical improvement of the present invention is that: the adaptive calibration of the coordinate reference of the mobile phone case product in step five includes the following steps: Obtain the reference origin position, reference axis direction, and spatial relationship deviation of the positioning holes for each product's candidate reference coordinate system; The origin calibration amount is calculated based on the positional deviation between the origin of each product reference candidate coordinate system and the origin of the design product coordinate reference, and the direction calibration amount is calculated based on the angular deviation between the reference axis direction of each product reference candidate coordinate system and the reference axis direction of the design product coordinate reference. Calculate the benchmark consistency value based on the spatial relationship deviation of the positioning holes corresponding to the candidate benchmark coordinate systems of each product. Based on the origin calibration value, direction calibration value and reference consistency value, the candidate reference coordinate systems of each product are compared to determine the candidate reference coordinate system of the target product. Based on the origin calibration and orientation calibration of the candidate coordinate system of the target product reference, the coordinates of each candidate point of the probability center of the positioning hole in the unified product coordinate space are corrected to obtain the calibrated product coordinate reference. Calculate the calibrated spatial position of each positioning hole based on the calibrated product coordinate reference, and compare the deviation between the calibrated spatial position and the designed positioning hole position.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention constructs a contour action energy field and a distance potential field inside the positioning hole, and further generates a center probability field, so that the effect of the positioning hole contour structure on the internal space can be expressed in the form of a continuous field. Thus, even when the positioning hole contour is elliptical or has local anomalies, the stable center position of the region inside the hole can still be stably determined, thereby improving the stability of the positioning hole center extraction process. Furthermore, by analyzing the contour action energy field, this invention identifies abnormal action areas in the positioning hole contour and suppresses the energy propagation in abnormal areas, thereby reducing the impact of burrs, missing edges, or local contour anomalies on the center calculation process. This allows the overall geometric features of the positioning hole to be expressed more stably in subsequent calculations, improving the reliability of center extraction. On the other hand, this invention establishes the drift coupling relationship between positioning holes by comprehensively analyzing the spatial relationship between multiple candidate probability centers of positioning holes, and generates multiple candidate product reference coordinate systems. Then, it determines the candidate target product reference coordinate system based on the stability of the spatial relationship, thereby achieving adaptive calibration of the coordinate reference of the mobile phone case product. Even when the size of the positioning hole drifts or the structure changes, it can still obtain stable product reference coordinates, thereby improving the overall accuracy of visual inspection and assembly positioning processes. Attached Figure Description

[0013] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0014] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0015] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0016] Please see Figure 1 As shown, the present invention provides a reference calibration method for the drift of positioning hole size in mobile phone cases, comprising: Step 1 involves acquiring the contour boundary data of multiple positioning holes on the phone case, establishing a contour effect energy field within the internal region of the positioning holes, and constructing a distance potential field based on the distance relationship from each position to the contour boundary. A center probability field for the positioning holes is then generated based on the contour effect energy field and the distance potential field. This step, by acquiring the contour boundary data of multiple positioning holes on the phone case, provides basic input data for subsequent analysis of the positioning hole structure. Building upon this, establishing a contour effect energy field within the internal region of the positioning holes transforms the influence of the positioning hole contour boundary on the internal space from discrete boundary information to continuous distribution information, allowing the overall geometric effect of the positioning hole contour to be expressed within the hole region. Simultaneously, constructing a distance potential field based on the distance relationship from each position to the contour boundary further characterizes the distance distribution state of different positions within the positioning hole relative to the contour boundary. The center probability field of the positioning holes is generated under the combined action of the contour effect energy field and the distance potential field, thus forming the center probability distribution results corresponding to each position within the positioning hole. This provides a unified data and analytical foundation for subsequent suppression of abnormal contour influences and screening of stable centers.

[0017] In this embodiment, for a single positioning hole on a mobile phone case, its contour boundary data is first acquired. Specifically, edge extraction can be performed on the surface image of the mobile phone case to obtain a set of boundary points for the positioning hole. The number of boundary points is, for example, 360 to 720. A connection relationship is established between adjacent boundary points according to the contour direction. Subsequently, the contour boundary data of the positioning hole is divided into contour segments according to the boundary connection relationship to obtain multiple contour segments, and the connection node relationship between each contour segment is determined. Specifically, the change in the tangential angle between adjacent boundary points can be used as the segmentation basis. When the average change in the angle between ten adjacent boundary points is greater than 8°, it is used as the boundary of the contour segment, thus obtaining, for example, 12 contour segments. The first and last boundary points of each contour segment are recorded as connection nodes. Based on this, the topological continuity parameter corresponding to each contour segment is calculated according to the connection node relationship between each contour segment to characterize the continuity of each contour segment in the overall contour structure. The connection integrity between a certain contour segment and its adjacent contour segments can be normalized to 0 to 1. The value of a complete connection without breaks is close to 1, and the value of a partial break is close to 0.3 to 0.5.

[0018] Secondly, after obtaining the topological continuity parameters, the length weight parameters corresponding to each contour segment are calculated based on the boundary arc length of each contour segment. These length weight parameters are then coupled with the topological continuity parameters to obtain the segment action weight for each contour segment. Specifically, the arc length of each contour segment is divided by the total arc length of all contour segments to obtain the length weight parameter, which is then coupled and calculated as: segment action weight = 0.6 × topological continuity parameter + 0.4 × length weight parameter. For example, if the topological continuity parameter of a contour segment is 0.92 and the length weight parameter is 0.11, then the segment action weight is 0.596. Then, using each contour segment as the action response propagation unit, segmented response transmission is performed to each grid position within the positioning hole according to the segment action weight. The response transmission process between adjacent contour segments is constrained based on the connection node relationship between each contour segment to suppress the diffusion effect of topologically discontinuous contour segments on the grid positions within the internal region. Specifically, grid points with a spacing of 0.02 mm can be established inside the positioning hole, and attenuation propagation is performed from each contour segment to each internal grid point. The single-segment energy response value received by a certain grid point can be taken as: Segment action weight × exp(-d / 0.15 mm); Where d is the shortest distance from the grid position to the corresponding contour segment, in millimeters, and 0.15 mm is the energy propagation attenuation coefficient. When there is a break in the connection node between adjacent contour segments, the cross-segment propagation coefficient is limited to 0.2; when the connection is complete, it is taken as 1.0. Then, the segmented energy responses formed by each contour segment are superimposed to generate the contour effect energy field of the internal region of the positioning hole. That is, the energy response values ​​of all contour segments to the same grid point are accumulated to obtain the contour effect energy field value of that grid point.

[0019] After obtaining the contour effect energy field, a distance potential field is constructed simultaneously based on the distance relationship from each position to the contour boundary. Specifically, the minimum distance and average distance from each grid point inside the positioning hole to all contour boundary points can be calculated, and the calculation is normalized according to the distance potential field value = minimum distance ÷ average distance, so that the area with a more balanced distance distribution has a higher distance potential field value.

[0020] In this embodiment, the minimum distance value represents the minimum Euclidean distance from the grid position to all boundary points of the positioning hole outline, and the average distance value represents the arithmetic mean of the distances from the grid position to all boundary points of the outline. This ratio reflects the degree of uniformity in the distance distribution from the position to the outline boundary. When the difference in distances from the position to each boundary point is small, the difference between the average distance value and the minimum distance value decreases, thus making the distance potential field value close to 1. When the distance distribution is uneven, the distance potential field value decreases, thereby quantifying the degree of distance uniformity in the internal region of the positioning hole.

[0021] Subsequently, the energy response gradient at each location inside the positioning hole is calculated based on the contour action energy field, and the distance response gradient at each location inside the positioning hole is calculated based on the distance potential field. Specifically, the lateral and longitudinal gradients can be calculated using the adjacent grid difference method. Then, the probability transfer direction corresponding to each location is determined based on the energy response gradient and the distance response gradient, and a probability transfer relationship matrix is ​​established in the region inside the positioning hole. The probability transfer direction can be set as the weighted composite direction of the reverse direction of the energy response gradient and the positive direction of the distance response gradient, where the weight of the energy response gradient is 0.55 and the weight of the distance response gradient is 0.45. The probability transfer relationship matrix is ​​established based on the transfer ratio of the grid point to the adjacent eight neighboring grid points.

[0022] Based on the above, neighborhood probability transfer calculation is performed in the internal region of the positioning hole according to the probability transfer relationship matrix, so that the probability value of each position is progressively accumulated to the adjacent position according to the corresponding probability transfer direction; specifically, the initial probability value can be set to 1, and neighborhood probability transfer is performed 6 times consecutively; then, during the probability transfer process, the probability value received at each position is accumulated and calculated, and the accumulated probability value of each position is arranged according to the corresponding spatial position to form a probability accumulation matrix, thus obtaining the probability accumulation matrix of each grid point in the hole; then, the probability density value of each position inside the positioning hole is calculated according to the probability accumulation matrix, and the probability density change amplitude is calculated according to the spatial gradient relationship between the probability density values ​​of each position. The region where the probability density change amplitude is lower than the probability stability threshold is determined as the probability stable region. Specifically, the probability density change amplitude can be defined as the average value of the difference between the probability density of a grid point and its eight neighboring probability densities. In this embodiment, the probability stability threshold is taken as 0.08; when the probability density change amplitude of more than 9 consecutive grid points in a certain region is lower than 0.08, the region is determined as the probability stable region. Finally, a central probability field is established for the internal region of the positioning hole based on the probability density values ​​of each location within the probability stable region. The probability density distribution results of each spatial location in the central probability field are used to characterize the concentration of the corresponding location as a candidate location for the positioning hole center, and serve as the input basis for screening candidate probabilities in the subsequent step three. That is, the probability density values ​​of each grid point within the probability stable region are used as the high probability distribution area of ​​the central probability field, thus obtaining the basic input that connects with the identification of abnormal action areas in the subsequent step two, the determination of distance equalization areas in the subsequent step three, and the screening of candidate probabilities.

[0023] Step 2: Analyze the continuity of energy changes and the consistency of propagation direction in each region of the positioning hole contour boundary based on the contour action energy field analysis. Identify abnormal action regions and perform energy attenuation processing on these regions to obtain effective contour regions. Among them, the consistency of propagation direction is used to characterize the degree of directional offset of adjacent regions of the contour boundary when transmitting the response toward the interior region of the positioning hole. Specifically, it is determined by comparing the angle difference between the corresponding main propagation directions of adjacent contour segments. When the angle difference between the corresponding main propagation directions of adjacent contour segments is not greater than the preset direction consistency threshold, it is determined that the adjacent contour segments meet the propagation direction consistency. This step, based on the contour action energy field established in step one, analyzes the continuity of energy changes and the consistency of propagation direction in each region of the positioning hole contour boundary. This allows for the differentiation between contour boundary regions that have a stable representation effect on the overall contour morphology and abnormal action regions caused by burrs, missing edges, or local contour anomalies. Abnormal action regions typically disrupt the continuous propagation of contour action within the hole space and cause local interference to subsequent center determination. Therefore, energy attenuation processing of abnormal action regions essentially reduces the influence of this part of the contour boundary on the internal space determination result. Through this processing, the interference of local abnormal contours can be weakened while preserving the main geometric contour action of the positioning hole, thereby obtaining an effective contour region that better reflects the overall geometric morphology of the positioning hole. This provides a more stable contour basis for subsequent distance analysis and center selection based on the effective contour region.

[0024] Specifically, after obtaining the contour energy field of the internal region of the positioning hole, the closed traversal order around the contour boundary of the positioning hole is determined according to the connection node relationship between each contour segment, and the boundary energy response sequence corresponding to each contour segment along the closed traversal order is obtained based on the contour energy field. Specifically, the 12 contour segments on the contour boundary of the positioning hole are arranged end-to-end according to the connection node relationship to form a clockwise closed traversal order; the energy response values ​​of 15 consecutive sampling points in the boundary neighborhood of each contour segment are extracted to form the corresponding boundary energy response sequence. Subsequently, forward closed traversal is performed on each contour segment according to the closed traversal order, and reverse closed traversal is performed according to the connection node relationship between each contour segment to obtain the forward closed sequence and reverse closed sequence corresponding to each contour segment. Forward closed traversal records the connection node position segment by segment according to the closed traversal order, and reverse closed traversal records the connection node position segment by segment in the opposite direction, thereby obtaining the forward closed sequence and reverse closed sequence corresponding to each contour segment.

[0025] Based on the forward and reverse closure sequences corresponding to each contour segment, the node consistency, arc continuity, and positional overlap are calculated. Simultaneously, based on the gradient principal direction pointing from the energy response value within the boundary neighborhood of each contour segment to the internal region of the positioning hole, the principal propagation direction of each contour segment is determined, and the angle difference between the principal propagation directions of adjacent contour segments is calculated. When the angle difference is no greater than 12°, the adjacent contour segment pair is determined as a propagation direction consistency pair, and the propagation direction consistency parameter is calculated based on the proportion of adjacent contour segment pairs satisfying the propagation direction consistency condition to the total number of adjacent contour segment pairs. Subsequently, the propagation direction consistency parameter, along with the node consistency, arc continuity, and positional overlap, are used to characterize the closed stable state of the contour segment.

[0026] The self-consistent closure parameters of each contour segment are calculated based on node consistency, arc continuity, and positional overlap. Specifically, the proportion of corresponding node position differences between the forward and reverse closure sequences being less than 0.03 mm is used as node consistency; the proportion of absolute values ​​of energy response change rates between adjacent sampling points being less than 0.12 is used as arc continuity; and the proportion of the spatial overlap length between the forward and reverse closure sequences to the total length of the contour segment is used as positional overlap. The self-consistent closure parameter is then calculated as: 0.4 × node consistency + 0.35 × arc continuity + 0.25 × positional overlap. Next, the cooperative stability parameters between contour segments are calculated based on the closure traversal order and the connection node relationships between adjacent contour segments. Segment pairs with energy response differences at the connection nodes of adjacent contour segments less than 0.08 and connection direction angles less than 10° are considered cooperatively stable, and the cooperative stability parameters are calculated based on the proportion of adjacent segment pairs meeting these conditions to the total number of adjacent segment pairs. Next, the closure anomaly parameters of each contour segment are calculated based on the self-consistent closure parameters and the cooperative stability parameters. The closure anomaly parameters can be taken as 1 - (0.6 × self-consistent closure parameter + 0.4 × cooperative stability parameter). The closure threshold is obtained experimentally. In this embodiment, the closure threshold is set to 0.42, which is obtained by statistically analyzing the closure anomaly parameters of 20 sets of mobile phone case positioning hole samples. In the 20 samples, the abnormal closure parameter distribution ranged from 0.08 to 0.38 for normal contour segments, while the abnormal closure parameter distribution ranged from 0.45 to 0.71 for abnormal contour segments with burrs or missing edges. Therefore, the boundary value of 0.42 between the distribution intervals of the two types of samples is taken as the closing threshold.

[0027] When the closure anomaly parameter of a certain contour segment is greater than 0.42, the abnormal contour segment is determined based on the comparison result between the closure anomaly parameter and the closure threshold, and the corresponding abnormal action area is determined based on the spatial position of the abnormal contour segment on the boundary of the positioning hole contour; for example, the closure anomaly parameter of the 4th contour segment is 0.57, then its corresponding boundary area is determined as the abnormal action area.

[0028] After identifying the anomalous action area, an isolation boundary is determined around the anomalous action area based on its spatial location on the contour boundary of the positioning hole. A local isolation zone for anomalous energy is then established based on the area between the isolation boundary and the anomalous action area. Specifically, the isolation boundary can be extended by 0.10 mm before and after the anomalous action area along the contour, forming a local isolation zone for anomalous energy between the isolation boundary and the anomalous action area. Subsequently, based on the distribution of the local isolation zone in the contour's energy field, the energy propagation path from the anomalous action area towards the interior of the positioning hole is restricted, while retaining the energy propagation path along the contour boundary of the positioning hole. This reduces the propagation coefficient from the local isolation zone towards the interior of the positioning hole from 1.0 to 0.18, while maintaining the propagation coefficient along the contour boundary of the positioning hole at 0.85. This restricts the diffusion of the anomalous action area into the hole while preserving the continuous propagation capability along the main contour.

[0029] The energy guiding boundary is determined based on the non-abnormal contour boundary region adjacent to the abnormal action region. The propagation direction of the abnormal energy is determined based on the continuity of the energy response of the energy guiding boundary in the contour action energy field. Specifically, the nearest non-abnormal contour boundary region on both sides of the abnormal action region can be selected as the energy guiding boundary, and the side with the smaller absolute value of the energy response change rate is determined as the preferred propagation direction; for example, if the average change rate of the left guiding boundary is 0.06 and that of the right is 0.14, the propagation direction is determined to be towards the left guiding boundary. The energy response within the local isolation zone of the abnormal energy is transferred to the corresponding non-abnormal contour boundary region according to the propagation direction. The energy propagation path of each region of the positioning hole contour boundary is updated based on the transferred energy response to obtain the updated contour action energy field. 60% of the remaining energy response within the local isolation zone of the abnormal energy can be transferred to the corresponding non-abnormal contour boundary region by distance attenuation, while the remaining 40% attenuates and dissipates within the isolation boundary. After the transfer is completed, the energy propagation path of all contour boundary regions is recalculated to obtain the updated contour action energy field. The updated contour action energy field can be used as the input basis for reconstructing the distance potential field in the subsequent step three. After reconstructing the distance potential field, the energy response gradient of each position inside the positioning hole is recalculated based on the updated contour action energy field, and jointly analyzed with the center probability field generated in step one to ensure that the energy distribution on which the subsequent candidate point selection of probability centers is based is consistent with the current effective contour region.

[0030] Step 3: Reconstruct the distance potential field based on the effective contour region. Determine the distance equilibrium region based on the degree of distance balance from each position inside the positioning hole to the contour boundary, and combine this with the center probability field to filter and obtain the probability center candidate points for each positioning hole. After suppressing the abnormal effect region, this step reconstructs the distance potential field based on the effective contour region, which allows the expression of distance relationship to reflect the main structure of the positioning hole more, rather than being affected by local abnormal contours. Based on this, determining the distance equilibrium region based on the degree of distance balance from each position inside the positioning hole to the contour boundary can identify internal regions with more balanced geometric distance relationships, making these regions more suitable as candidate regions for stable centers. Combining this with the center probability field for filtering can integrate the center stability distribution information obtained in Step 1 with the distance equilibrium information obtained based on the effective contour region, so that the filtering result takes into account both the stability of contour effects and the balance of distance relationships, and finally obtains the probability center candidate points for each positioning hole. This ensures that the center extraction result in the case of positioning hole size drift, ellipticization, or local contour anomalies remains consistent with the effective contour region and the distance equilibrium region.

[0031] Specifically, based on the identification of abnormal action areas and energy attenuation processing already completed in the aforementioned embodiments, and the resulting effective contour area, a distance potential field is reconstructed on top of this effective contour area. Specifically, a regular grid with a spacing of 0.02 mm can be established within the area inside the positioning hole. For each grid position, the shortest distance and average distance to all contour boundary points within the effective contour area are calculated, and normalized according to the formula: distance potential field value = shortest distance value ÷ average distance value. For example, if the shortest distance to the effective contour area at a certain grid position is 0.42 mm and the average distance is 0.56 mm, then the distance potential field value at that position is 0.75. After calculating all grid positions in this way, a reconstructed distance potential field is formed. Subsequently, the distance response values ​​corresponding to each position inside the positioning hole are obtained based on the reconstructed distance potential field. Based on the distance distribution relationship formed by the distance response values ​​in the area inside the positioning hole, multiple distance isopleth regions are determined. Specifically, the distance response values ​​can be divided into layers according to each 0.05 interval. The grid positions with distance response values ​​in the intervals of 0.70 to 0.75, 0.75 to 0.80, and 0.80 to 0.85 are divided into different distance isopleth regions.

[0032] Secondly, after obtaining multiple distance isopleth regions, the corresponding distance closed loop structure is determined based on the spatial continuity and closed distribution relationship of each distance isopleth region within the positioning hole's internal region. Specifically, adjacency connectivity analysis can be performed on each distance isopleth region. When the grid positions within the same interval are continuously connected under the eight-neighbor condition and form a closed distribution with their ends enclosing each other, the region is determined as a distance closed loop structure. For example, if a continuous closed strip-shaped region is formed around the center of the positioning hole within the interval of distance response values ​​from 0.80 to 0.85, then this strip-shaped region corresponds to a distance closed loop structure. Then, the ring stability parameters corresponding to each distance closed loop structure are calculated based on the distribution range of each distance closed loop structure along the internal region of the positioning hole. Specifically, the ring width fluctuation rate and the ring continuity rate can be used to characterize this. The ring width fluctuation rate is defined as the difference between the maximum and minimum local width values ​​in different angular directions of the same distance closed loop structure divided by the average width. The ring continuity rate is defined as the proportion of the continuous closed arc length to the theoretical closed perimeter. The ring stability parameter is then calculated as 0.5 × (1 - ring width fluctuation rate) + 0.5 × ring continuity rate. For example, if the ring width fluctuation rate of a certain distance closed loop structure is 0.18 and the ring continuity rate is 0.91, then its ring stability parameter is 0.865.

[0033] After obtaining the ring stability parameters of each distance closed loop structure, the inter-loop consistency parameter is calculated based on the spacing variation relationship between adjacent distance closed loop structures. Specifically, the radial spacing between two adjacent distance closed loop structures in multiple angular directions can be measured, for example, every 15°, resulting in 24 sets of spacing values. Then, the average spacing and standard deviation of these spacing values ​​are calculated and normalized according to the formula: inter-loop consistency parameter = 1 - (standard deviation ÷ average spacing). If the average spacing between two adjacent distance closed loop structures is 0.06 mm and the standard deviation is 0.009 mm, the corresponding inter-loop consistency parameter is 0.85. Next, the distance structure stable region is determined based on the ring stability parameter and the inter-loop consistency parameter, and the distance structure stable region is defined as the distance equilibrium region inside the positioning hole. Specifically, the internal region enclosed by adjacent distance closed loop structures with a ring stability parameter of not less than 0.82 and an inter-loop consistency parameter of not less than 0.80 can be defined as the distance structure stable region. In this embodiment, the central layer closed region that meets the above conditions is defined as the distance equilibrium region inside the positioning hole. The ring stability parameter threshold of 0.82 and the inter-ring consistency parameter threshold of 0.80 were obtained by statistical analysis of 20 sets of mobile phone case positioning hole samples, which can take into account the stable identification requirements under the conditions of elliptical holes and local defect holes.

[0034] Finally, after determining the distance equilibrium region, the candidate probabilities of each positioning hole are obtained by combining the central probability field. Specifically, the central probability field established in the previous embodiment can be superimposed on the distance equilibrium region obtained in this embodiment. The probability density values ​​corresponding to each grid position in this region are sorted, and the continuous grid clusters with probability density values ​​in the top 10% are selected as candidate central regions. Then, the geometric mean coordinates of all grid positions in the candidate central region are calculated to obtain the candidate probabilities of the positioning hole. For example, if the candidate central region of a positioning hole contains 16 continuous grid positions with an average coordinate value of (1.245 mm, 0.873 mm), then this coordinate is used as the candidate probabilities of the positioning hole. Thus, based on the aforementioned contour action energy field update results and central probability field, this embodiment further obtains stable input results that can be mapped to a unified product coordinate space and used to calculate drift coupling relationships in the subsequent step four by reconstructing the distance potential field, extracting the distance closed loop structure, and determining the distance equilibrium region.

[0035] Step four involves mapping the probability center candidate points of each positioning hole to a unified product coordinate space. Based on the relative spacing, orientation, and center stability of each positioning hole, the drift coupling relationship between them is calculated, generating multiple product reference candidate coordinate systems. While step three has already yielded relatively stable probability center candidate points for each positioning hole, the center results of a single positioning hole may still exhibit some local deviation. Therefore, it is necessary to map the probability center candidate points of each positioning hole to a unified product coordinate space and analyze the overall spatial relationship between multiple positioning holes under a unified coordinate reference. By calculating the drift coupling relationship between positioning holes based on their relative spacing, orientation, and center stability, the interrelationships exhibited by multiple positioning holes under dimensional drift can be reflected, rather than simply using the center results of a single positioning hole in isolation. Generating multiple product reference candidate coordinate systems on this basis preserves the reference results that may be formed under different combinations of spatial relationships, providing a basis for further comparison of the stability and rationality of different candidate coordinate systems, thereby avoiding the overall product reference instability caused by the superposition of deviations in the center of a single positioning hole.

[0036] The outer contour boundary data of the phone case is acquired, and boundary line segments on the phone case frame are extracted based on this data. The reference direction of the phone case frame is determined based on the extension direction of these boundary line segments. Specifically, the outer contour of the phone case can be edge-extracted under the same image coordinates as the aforementioned positioning hole contour extraction, resulting in a continuous set of outer contour boundary points. Then, the outer contour is divided into multiple boundary line segments according to the local direction changes of these continuous boundary points. When the direction deviation of 20 adjacent boundary points after fitting a straight line is no greater than 3°, they are grouped into the same boundary line segment. For the two main boundary line segments formed by the long side region of the phone case, their extension direction angles are calculated. For example, if one is 1.8° and the other is 2.4°, the average direction of the two, 2.1°, is taken as the reference direction of the phone case frame. Subsequently, the four candidate probability centers of the positioning holes obtained in the aforementioned embodiments are mapped to a unified product coordinate space. For example, the coordinates of the four candidate probability centers of the positioning holes in the space are (12.36 mm, 8.42 mm), (38.91 mm, 8.57 mm), (12.48 mm, 66.13 mm) and (39.05 mm, 66.32 mm), respectively.

[0037] The probability center candidate points of each positioning hole are projected along the reference direction of the phone case frame. The arrangement order of each positioning hole is determined based on the projection position of each probability center candidate point. The spacing change between adjacent positioning holes is calculated based on the projection spacing between adjacent probability center candidate points. Specifically, each probability center candidate point can be decomposed along the reference direction of the phone case frame and its perpendicular direction to obtain the projection coordinate value along the reference direction of the phone case frame. For example, if the projection coordinates of the four positioning holes are 12.65 mm, 39.18 mm, 12.77 mm, and 39.31 mm respectively, then the arrangement order of the positioning holes can be determined as the first positioning hole, the third positioning hole, the second positioning hole, and the fourth positioning hole according to the projection coordinates from smallest to largest. Then, the difference between adjacent projection coordinates is calculated to obtain the projection spacing between adjacent positioning holes. Based on the projection coordinates, the four positioning holes can be divided into two columns arranged along the reference direction of the phone case frame. The group of positioning holes with smaller projection coordinates forms the left column, and the group of positioning holes with larger projection coordinates forms the right column. The left column contains the first positioning hole and the third positioning hole, with an average projected coordinate of 12.71 mm; The right column contains the second and fourth positioning holes, with an average projected coordinate of 39.25 mm; Therefore, the average projected spacing between the two columns is approximately 26.54 mm, and the spacing variation is obtained by comparing it with the designed projected spacing of 26.80 mm.

[0038] Further comparison with the designed positioning hole projection spacing of 26.80 mm yielded corresponding spacing changes of 0.26 mm and 0.24 mm, respectively. Meanwhile, considering the probability density peak value or local concentration of the central probability field corresponding to each positioning hole probability center candidate point in the aforementioned embodiments, the center stability is calculated by the ratio between the corresponding probability density peak value in the central probability field and the mean probability density value of the neighborhood. A larger ratio indicates a higher degree of stability of the probability center candidate point in the central probability field. In this embodiment, the center stability of the four positioning holes are 0.93, 0.91, 0.95 and 0.90, respectively, providing a unified input for subsequent calculations.

[0039] The displacement direction and amount of each positioning hole are calculated based on the positional deviation between the candidate probability center point of each positioning hole and the designed positioning hole position. The drift trend parameters of each positioning hole along the reference direction of the phone case frame are determined based on the arrangement order, spacing variation, displacement direction, and displacement amount. These drift trend parameters characterize the comprehensive displacement change state of the positioning holes in the reference direction of the phone case frame and its perpendicular direction. Specifically, the designed positioning hole positions can be pre-loaded into a unified product coordinate space, for example, designed positions of (12.50 mm, 8.50 mm), (39.20 mm, 8.50 mm), (12.50 mm, 66.20 mm), and (39.20 mm, 66.20 mm). Then, the vector difference between the candidate probability center point of each positioning hole and the designed positioning hole position is calculated to obtain the displacement direction and amount. For example, the displacement vector of the first positioning hole is (-0.14 mm, -0.08 mm), its displacement amount is 0.16 mm, and its displacement direction is -150° relative to the reference direction of the phone case frame. Combining the aforementioned arrangement order and spacing variation, the processing drift trend value is calculated as follows: 0.5 × displacement component along the reference direction of the phone case frame + 0.3 × vertical displacement component + 0.2 × spacing variation. For example, the displacement component along the reference direction of the first positioning hole is -0.13 mm, the vertical displacement component is -0.09 mm, and the spacing variation is 0.26 mm; therefore, the processing drift trend of this positioning hole is -0.021 mm. After performing similar calculations for all positioning holes, if the difference in processing drift trend value of positioning holes in the same column is no greater than 0.05 mm, and the difference in the included angle of displacement direction of positioning holes in the same row is no greater than 8°, then the positioning holes can be considered to have consistent processing drift characteristics in the current batch.

[0040] The drift coupling relationship between the positioning holes is determined based on their relative spacing, directional relationship, center stability, and processing drift trend. Multiple product reference candidate coordinate systems are generated based on these drift coupling relationships, and the directional deviation between each product reference candidate coordinate system and the reference direction of the phone case frame is calculated. The arrangement order of the product reference candidate coordinate systems is determined based on the directional deviation. Specifically, candidate combinations can be formed using combinations of two positioning holes, three positioning holes, and all positioning holes. For each candidate combination, the corresponding relative spacing deviation, directional deviation, average center stability, and average drift trend consistency are calculated. The drift coupling relationship corresponding to the combination is determined by the coupling score: 0.35 × spacing consistency + 0.25 × directional consistency + 0.20 × average center stability + 0.20 × processing drift trend consistency. For example, the coupling score of the combination consisting of the first, second, and fourth positioning holes is 0.914, and the coupling score of the combination consisting of the first, third, and fourth positioning holes is 0.903, thus generating corresponding product reference candidate coordinate systems. Subsequently, the angle between the reference axis direction of each product's candidate coordinate system and the reference direction of the phone case frame is calculated to obtain the direction deviation. For example, if the direction deviations of two candidate coordinate systems are 0.9° and 1.4° respectively, the former is prioritized. This results in multiple product candidate coordinate systems sorted by direction deviation, which serve as direct inputs for further determining the target product candidate coordinate system and performing product coordinate reference calibration in subsequent step five.

[0041] Step 5: Determine the target product reference candidate coordinate system based on the spatial relationship deviation and center stability of the positioning holes corresponding to each product reference candidate coordinate system. Then, calculate the coordinate offset and direction rotation based on the spatial relationship deviation between this coordinate system and the design product coordinate reference. Correct the coordinates of the probabilistic center candidate points of the positioning holes in the unified product coordinate space to obtain the calibrated phone case product coordinate reference. This step, based on the multiple product reference candidate coordinate systems generated in Step 4, requires further comparison of the degree of deviation of different candidate results in the spatial relationship of the positioning holes and the stability of the corresponding center results, thereby determining the most suitable target product reference for the actual working of the current phone case product. A candidate coordinate system for the product reference is established. Based on this, the coordinate offset and direction rotation are calculated according to the spatial relationship deviation between this coordinate system and the design product coordinate reference. This clarifies the spatial changes that have occurred in the current actual product reference relative to the design state. Further coordinate correction is performed on the candidate points of the probabilistic center of the positioning hole in the unified product coordinate space. This can compensate the aforementioned spatial deviation into the actual product coordinate reference used, and finally obtain the calibrated mobile phone case product coordinate reference. This allows the reference coordinates used in subsequent testing or assembly processes to more accurately reflect the actual structural state after the positioning hole size drift, thereby improving the consistency and accuracy of subsequent testing positioning and assembly positioning.

[0042] The origin position, axis direction, and spatial deviation of the positioning holes corresponding to each product's candidate reference coordinate system are obtained. Specifically, the three candidate reference coordinate systems obtained in the previous embodiment are denoted as the first candidate, the second candidate, and the third candidate, respectively. The first candidate has an origin position of (25.68 mm, 37.42 mm), an axis direction of 2.6°, and a spatial deviation of 0.18 mm for the positioning holes; the second candidate has an origin position of (25.74 mm, 37.36 mm), an axis direction of 3.1°, and a spatial deviation of 0.24 mm for the positioning holes; and the third candidate has an origin position of (25.61 mm, 37.48 mm), an axis direction of 1.9°, and a spatial deviation of 0.21 mm for the positioning holes. The product coordinate reference is pre-given by the product design data in this embodiment, with an origin position of (25.50 mm, 37.50 mm) and an axis direction of 0°. Based on this, the correspondence between each candidate coordinate system of the product reference and the coordinate reference of the designed product is calculated, providing input for the next step of calculating the origin calibration amount and the direction calibration amount.

[0043] The origin calibration amount is calculated based on the positional deviation between the origin of each candidate product reference coordinate system and the origin of the design product coordinate reference. The orientation calibration amount is calculated based on the angular deviation between the reference axis direction of each candidate product reference coordinate system and the reference axis direction of the design product coordinate reference. Finally, the reference consistency value is calculated based on the spatial relationship deviation of the positioning holes corresponding to each candidate product reference coordinate system. Specifically, the origin calibration amount is defined as the two-dimensional displacement vector and its magnitude between the candidate origin position and the design origin position. For example, the two-dimensional displacement vector of the first candidate is (0.18 mm, -0.08 mm), and its magnitude is 0.197 mm. The orientation calibration amount is defined as the angular deviation of the candidate reference axis direction relative to the design reference axis direction. For example, the orientation calibration amount of the first candidate is 2.6°. The datum consistency value is calculated based on the spatial relationship deviation of the positioning holes, specifically using the formula: Datum Consistency Value = 1 - (Spatial Relationship Deviation of Positioning Holes ÷ 0.50), where 0.50 mm is the normalized datum value set in this embodiment based on the upper limit of the sample machining tolerance; for example, if the spatial relationship deviation of the positioning holes in the first candidate is 0.18 mm, then its datum consistency value is 0.64, the second candidate is 0.52, and the third candidate is 0.58. Thus, the corresponding origin calibration value, direction calibration value, and datum consistency value are obtained for the three product datum candidate coordinate systems.

[0044] The candidate coordinate systems of each product are compared based on the origin calibration value, direction calibration value, and reference consistency value to determine the candidate coordinate system of the target product. Specifically, to ensure that the comparison process is fully transparent, a unified comparison value is constructed in this embodiment: comparison value = 0.4 × normalized value of origin calibration value + 0.3 × normalized value of direction calibration value + 0.3 × (1 - reference consistency value).

[0045] The weighting coefficients of 0.4, 0.3, and 0.3 were obtained through statistical analysis of the assembly errors of 15 batches of mobile phone case samples. In the statistical sample, the contribution of origin offset to the overall assembly error is about 40%, the contribution of direction rotation error is about 30%, and the contribution of positioning hole spatial relationship stability is about 30%. Therefore, the above weighting coefficients are used for weighted comparison.

[0046] The origin calibration modulus is normalized to 0.30 mm, and the orientation calibration is normalized to 5°. The calculated comparison values ​​are: 0.4 × (0.197 ÷ 0.30) + 0.3 × (2.6 ÷ 5) + 0.3 × (1 - 0.64) = 0.477; 0.589; and 0.448. Therefore, the third candidate with the smallest comparison value is selected as the target product's baseline candidate coordinate system. Through the above comparison method, the deviations between the candidate coordinate systems and the design state, as well as the stability of their corresponding spatial relationships, are compared to determine the target product's baseline candidate coordinate system corresponding to the logic generated in step four.

[0047] Finally, the coordinates of each candidate point of the probability center of the positioning hole in the unified product coordinate space are corrected according to the origin calibration and direction calibration of the candidate coordinate system corresponding to the target product reference. This yields the calibrated product coordinate reference for the phone case. The calibrated spatial position of each positioning hole is then calculated based on the calibrated product coordinate reference, and the deviation between the calibrated spatial position and the designed positioning hole position is compared. Specifically, the coordinates of the four candidate points of the probability center of the positioning hole in the aforementioned embodiment are used, for example, (12.36 mm, 8.42 mm), (38.91 mm, 8.57 mm), (12.48 mm, 66.13 mm), and (39.05 mm, 66.32 mm), respectively. The third candidate is used as the candidate coordinate system for the target product reference, with its corresponding origin calibration of (0.11 mm, -0.02 mm) and direction calibration of 1.9°. First, using the third candidate reference origin position as the rotation center, rotate the four probability center candidate points in the opposite direction by 1.9°, and then subtract the translation amount of (0.11 mm, -0.02 mm) to complete the coordinate correction and obtain the calibrated product coordinate reference. Based on this, the calibrated spatial positions of the four positioning holes are calculated. For example, the calibrated coordinates of the first positioning hole are (12.49 mm, 8.51 mm), the second positioning hole is (39.18 mm, 8.49 mm), the third positioning hole is (12.52 mm, 66.19 mm), and the fourth positioning hole is (39.22 mm, 66.18 mm). The deviations are then compared with the designed positioning hole positions (12.50 mm, 8.50 mm), (39.20 mm, 8.50 mm), (12.50 mm, 66.20 mm), and (39.20 mm, 66.20 mm), respectively. The residual deviations of the four positioning holes are found to be 0.014 mm, 0.022 mm, 0.022 mm, and 0.028 mm, respectively. Thus, this embodiment completes the entire process from comparing candidate coordinate systems for the product reference, determining the candidate coordinate system for the target product reference, to forming the calibrated product coordinate reference, and can be directly connected with the probability center candidate point calculation results in the aforementioned embodiment.

[0048] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters and thresholds in the formulas are set by those skilled in the art according to the actual situation.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A reference calibration method for addressing the size drift of positioning holes in mobile phone cases, characterized in that, include: Step 1: Obtain the contour boundary data of multiple positioning holes on the phone case, establish a contour action energy field in the internal region of the positioning holes, and construct a distance potential field based on the distance relationship from each position to the contour boundary. Generate the center probability field of the positioning holes based on the contour action energy field and the distance potential field. Step 2: Based on the energy field analysis of the contour effect, analyze the continuity of energy changes and the consistency of propagation direction in each region of the positioning hole contour boundary, identify abnormal action areas, and perform energy attenuation processing on the abnormal action areas to obtain the effective contour area. Step 3: Reconstruct the distance potential field based on the effective contour area, determine the distance balance area according to the degree of distance balance from each position inside the positioning hole to the contour boundary, and combine the center probability field to screen and obtain the probability center candidate points of each positioning hole. Step 4: Map the probability center candidate points of each positioning hole to a unified product coordinate space. Calculate the drift coupling relationship between the positioning holes based on the relative spacing, orientation, and center stability of each positioning hole, and generate multiple product reference candidate coordinate systems. Step 5: Determine the target product reference candidate coordinate system based on the spatial relationship deviation of the positioning holes and the center stability corresponding to each product reference candidate coordinate system. Calculate the coordinate offset and direction rotation based on the spatial relationship deviation between this coordinate system and the design product coordinate reference. Correct the coordinates of the probabilistic center candidate points of the positioning holes in the unified product coordinate space to obtain the calibrated mobile phone case product coordinate reference.

2. The reference calibration method for the positioning hole size drift of a mobile phone case according to claim 1, characterized in that, The establishment of the contour effect energy field in step one includes the following steps: The contour boundary data of the positioning hole is divided into contour segments according to the boundary connection relationship to obtain multiple contour segments, and the connection node relationship between each contour segment is determined. The topological continuity parameters of each contour segment are calculated based on the connection node relationship between each contour segment to characterize the degree of continuity of each contour segment in the overall contour structure. The length weight parameter corresponding to each contour segment is calculated based on the boundary arc length of each contour segment, and the length weight parameter is coupled with the topological continuity parameter to obtain the segment action weight corresponding to each contour segment. Each contour segment is used as an energy propagation unit. Segmented propagation is performed to the internal area of ​​the positioning hole according to the segment action weight. The energy propagation between adjacent contour segments is constrained according to the connection node relationship between each contour segment in order to suppress the diffusion effect of topologically discontinuous contour segments on the internal area. The segmented energy responses formed by each contour segment are superimposed to generate the contour effect energy field in the internal region of the positioning hole.

3. The reference calibration method for the positioning hole size drift of a mobile phone case according to claim 2, characterized in that, The generation of the central probability field in step one includes the following steps: The energy response gradient at each position inside the positioning hole is calculated based on the contour action energy field, and the distance response gradient at each position inside the positioning hole is calculated based on the distance potential field. The probability transfer direction corresponding to each position is determined based on the energy response gradient and the distance response gradient, and a probability transfer relationship matrix is ​​established in the internal region of the positioning hole. Based on the probability transfer relationship matrix, a neighborhood probability transfer calculation is performed in the area inside the positioning hole, so that the probability value of each position is progressively accumulated to the adjacent position according to the corresponding probability transfer direction; During the probability transmission process, the probability values ​​received at each location are accumulated and calculated, and the accumulated probability values ​​at each location are arranged according to their corresponding spatial locations to form a probability accumulation matrix; The probability density values ​​of each position inside the positioning hole are calculated based on the probability accumulation matrix, and the probability density change amplitude is calculated based on the spatial gradient relationship between the probability density values ​​of each position. The region where the probability density change amplitude is lower than the probability stability threshold is determined as the probability stable region. The central probability field of the internal region of the positioning hole is established based on the probability density values ​​of each location within the probability stable region.

4. The reference calibration method for the positioning hole size drift of a mobile phone case according to claim 1, characterized in that, Step two, the identification of abnormal action areas, includes the following steps: The closed traversal order around the boundary of the positioning hole is determined based on the connection node relationship between each contour segment, and the boundary energy response sequence corresponding to each contour segment along the closed traversal order is obtained based on the contour action energy field. Perform forward closure tracing on each contour segment according to the closure traversal order, and perform reverse closure tracing according to the connection node relationship between each contour segment to obtain the forward closure sequence and reverse closure sequence corresponding to each contour segment; Calculate the node consistency, arc continuity, and position overlap based on the forward and reverse closure sequences corresponding to each contour segment, and calculate the self-consistent closure parameters of each contour segment based on the node consistency, arc continuity, and position overlap. Calculate the cooperative stability parameters between each contour segment based on the closure traversal order and the connection node relationship between adjacent contour segments; The closure anomaly parameters of each contour segment are calculated based on the self-consistent closure parameters and the cooperative stability parameters. The abnormal contour segment is determined based on the comparison between the abnormal closure parameter and the closure threshold, and the corresponding abnormal action area is determined based on the spatial position of the abnormal contour segment on the boundary of the positioning hole contour.

5. A reference calibration method for addressing positioning hole size drift in mobile phone cases according to claim 1, characterized in that, Step two involves energy attenuation processing of the anomalous action area, including the following steps: The isolation boundary surrounding the abnormal action area is determined based on the spatial position of the abnormal action area on the boundary of the positioning hole, and a local isolation zone for abnormal energy is established based on the area between the isolation boundary and the abnormal action area. Based on the distribution location of the abnormal energy local isolation zone in the contour action energy field, the energy propagation path from the abnormal action area toward the interior region of the positioning hole is restricted, while the energy propagation path along the contour boundary of the positioning hole is retained; The energy guiding boundary is determined based on the non-abnormal contour boundary region adjacent to the abnormal action region, and the propagation direction of the abnormal energy is determined based on the continuity of the energy response of the energy guiding boundary in the contour action energy field. Based on the propagation direction, the energy response within the local isolation zone of abnormal energy is transferred to the corresponding non-abnormal contour boundary region. The energy propagation path of each region of the positioning hole contour boundary is updated based on the transferred energy response to obtain the updated contour action energy field.

6. A reference calibration method for addressing positioning hole size drift in mobile phone cases according to claim 1, characterized in that, Step three, determining the distance equilibrium region, includes the following steps: The distance response values ​​corresponding to each position inside the positioning hole are obtained based on the reconstructed distance potential field, and multiple distance equivalence regions are determined based on the distance distribution relationship formed by the distance response values ​​in the region inside the positioning hole. Based on the spatial continuity and closed distribution relationship of each distance equivalence region within the positioning hole area, the corresponding distance closed loop structure is determined; Calculate the ring stability parameters corresponding to each distance closed loop structure based on the distribution range of each distance closed loop structure along the internal region of the positioning hole; Calculate the inter-loop consistency parameters based on the spacing variation relationship between adjacent closed-loop structures; The distance structure stability region is determined based on the ring stability parameters and the inter-ring consistency parameters, and the distance structure stability region is defined as the distance equalization region inside the positioning hole.

7. A reference calibration method for addressing positioning hole size drift in mobile phone cases according to claim 1, characterized in that, Step four, which involves generating multiple candidate coordinate systems for product references, includes the following steps: Obtain the outer contour boundary data of the phone case, extract the boundary line segments on the phone case frame based on the outer contour boundary data, and determine the reference direction of the phone case frame based on the extension direction of the boundary line segments. Project the probability center candidate points of each positioning hole along the reference direction of the phone case frame, determine the arrangement order of each positioning hole according to the projection position of each probability center candidate point, and calculate the spacing change between adjacent positioning holes according to the projection spacing between adjacent probability center candidate points. The displacement direction and displacement amount of each positioning hole are calculated based on the positional deviation between the candidate probability center point of each positioning hole and the designed positioning hole position. The processing drift trend of each positioning hole along the reference direction of the mobile phone case frame is determined based on the arrangement order, spacing change, displacement direction and displacement amount. The drift coupling relationship between the positioning holes is determined based on the relative spacing, directional relationship, center stability, and machining drift trend among the positioning holes. Multiple product reference candidate coordinate systems are generated based on the drift coupling relationship, and the directional deviation between each product reference candidate coordinate system and the reference direction of the phone case frame is calculated. The arrangement order of each product reference candidate coordinate system is determined based on the directional deviation.

8. A reference calibration method for addressing positioning hole size drift in mobile phone cases according to claim 1, characterized in that, Step five involves adaptive calibration of the phone case product coordinate reference, which includes the following steps: Obtain the reference origin position, reference axis direction, and spatial relationship deviation of the positioning holes for each product's candidate reference coordinate system; The origin calibration amount is calculated based on the positional deviation between the origin of each product reference candidate coordinate system and the origin of the design product coordinate reference, and the direction calibration amount is calculated based on the angular deviation between the reference axis direction of each product reference candidate coordinate system and the reference axis direction of the design product coordinate reference. Calculate the benchmark consistency value based on the spatial relationship deviation of the positioning holes corresponding to the candidate benchmark coordinate systems of each product. Based on the origin calibration value, direction calibration value and reference consistency value, the candidate reference coordinate systems of each product are compared to determine the candidate reference coordinate system of the target product. Based on the origin calibration and orientation calibration of the candidate coordinate system of the target product reference, the coordinates of each candidate point of the probability center of the positioning hole in the unified product coordinate space are corrected to obtain the calibrated product coordinate reference. Calculate the calibrated spatial position of each positioning hole based on the calibrated product coordinate reference, and compare the deviation between the calibrated spatial position and the designed positioning hole position.

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